In the past there has been some disagreement among patients (and even some of their physicians) what chronic Migraine actually is.
Is it a different Migraine type? Or form? Or variant? Is chronic Migraine different from episodic Migraine, or a worse form of the same disease?
Until more is understood about the pathophysiology (how it happens inside the body) and epidemiology (who it happens to) of Migraine and chronic Migraine, we can only make educated assumptions based on the information we currently have.
Understanding these definitions is vital before patients can understand how chronification of Migraine occurs.
Definition of Migraine type
There are different types of Migraine — a genetic, neurologic disease – which have different and unique symptoms, and in some cases have been proven to have unique genetic markers. According to the ICHD-II, some Migraine types include:
- Migraine with aura
- Migraine without aura
- Common childhood precursors to Migraine
- Retinal Migraine
- Probable Migraine (when the physician is unsure of the diagnosis)
Definition of Migraine form
A Migraine form is a specific type of Migraine by ICHD-II definition which may have progressed or transformed. The form has changed, but the type remains the same.
Definition of Progression and/or Transformation: “Migraine progression or transformation should be understood as the potential for evolution to a different form.” (1) This frequently includes clinical transformation/progression to a different form, and back again. Progression and transformation of Migraine forms is not the same as a neurodegenerative disease in which the condition continues to worsen without chance of improvement.
Migraine forms may be somewhat overlapping and include:
- Increased frequency. Over time attacks may become more and more frequent, eventually resulting in chronification of Migraine (Migraine and headache 15 or more days a month).
- Alterations occur in the brain itself. Pain thresholds and pathways in the brain physically change. Termed Central Sensitization, this seems to be a risk factor for Migraines changing from episodic to chronic.
- Brain lesions may emerge. While this is sometimes considered a complication of Migraine disease, they do not usually result in deficit and are not typical.
Definition of Migraine variant
A Migraine variant (MV) is also known as a Migraine equivalent. It may resemble another disease or disorder such as stroke, but is a Migraine. “MV is therefore diagnosed by the history of paroxysmal symptoms with or without cephalgia and a prior history of migraine with aura, in the absence of other medical disorders that may contribute to the symptoms.” (2) A Migraine variant is not a primary or secondary headache type such as thunderclap headache, cluster headache, hemicrania continua or intracranial hypotension. “Chronic migraine and status migrainosus are not considered migraine variants” (3)
Examples of Migraine variants include:
Migraine complications: A complication of Migraine is generally defined as a condition that results from Migraine disease.
Examples of Migraine complications include:
- Chronic Migraine (Migraine or headache 15 or more days per month)
- Status Migrainosus (severe Migraine lasting more than 72 hrs)
- Persistent aura without infarction (aura without stroke that doesn’t go away)
- Migrainous infarction (stroke)
- Migraine triggered seizure